Diss.--Philosophie--Nashville, Tenn., 1981. / Contient quelques exemples musicaux. Bibliogr. p. 436-445.

<p>Collisions between FPSO and shuttle tanker in tandem offloading operation have caused a growing concern in the North Sea. Several recent contact incidents between FPSO/FSU and shuttle tanker have clearly demonstrated a high likelihood of contact between vessels in tandem offloading. The large masses involved, i.e. the high potential impact energy, make the collision risk large. Traditional ship/platform collision frequency modeling may not be applicable in the tandem offloading context. Moreover, offshore quantitative risk analyses generally focus more on technical aspects, little on human and organizational aspects. This leads to a hardware-dominated risk reduction approach, and it has been proved not to be effective to mitigate risks involved in complex marine operations in general.</p><p>Frequency modeling of collision between FPSO and shuttle tanker in offloading operation is carried out in this study. The collision frequency model is structured in two stages, i.e. the initiating stage and the recovery stage, where the former involves an uncontrolled forward movement of tanker, and the latter involves the recovery actions initiated from tanker and FPSO to avoid the collision.</p><p>In the <i>initiating </i>stage, this study focuses on tanker drive-off forward scenarios. Macroscopically, the frequency of tanker drive-off ahead during offshore loading and specifically during tandem offloading is portrayed by statistical data from an earlier study, recent SYNERGI incident data, and expert judgments made by tanker DP operators. Relatively high frequency values of tanker drive-off in tandem offloading are found. Microscopically, the tanker drive-off ahead scenario is investigated by examining 9 such events in tandem offloading based on investigation reports, interviews and discussions with individuals who directly or indirectly were involved. Findings reveal that in order to effectively reduce tanker drive-off in tandem offloading, efforts should be targeted on minimizing those failure prone situations, i.e. the excessive relative motions (termed as surging and yawing) between FPSO and tanker. A simulation-based study is carried out to quantitatively assess and effectively minimize the occurrence of excessive surging and yawing events. Horizontal motions of FPSO and tanker in tandem configuration are simulated via a state-of-the-art time-domain simulation code SIMO. Findings demonstrate that excessive surging and yawing events can be effectively minimized via measures such as minimizing FPSO surge and yaw motions in offloading, coordinating mean heading between FPSO and tanker, and using the dedicated DP software with the tandem loading function on tanker. Ultimately, these measures may provide a sound operational environment where the possibility of tanker drive-off can be minimized.</p><p>In the <i>recovery</i> stage, this study is focused on the recovery action initiated by the tanker DP operator. Possible recovery actions are identified and evaluated. Based on calibrated tanker motion simulations, the allowable time for DP operator to initiate recovery action, so that tanker can be stopped within a separation distance, e.g. 80 m to FPSO, is found to be critically short. A 3-stage information-decision-execution model is generalized to model the DP operator’s information processing stages regarding action initiation when in a drive-off scenario. Based on this human information-processing model, expert judgment by simulator trainer and questionnaire survey among shuttle tanker captains and DP officers are conducted, reasonable estimates of the time needed for action initiation are obtained. The estimates are found to be convergent to the facts in the incidents. Findings suggest that tanker DP operators in general need more time to initiate recovery action than the allowable time window, i.e. recovery failure is likely due to lack of reaction time. Two principal recommendations are proposed to reduce the recovery failure probability, i.e. to provide a longer time window for the operator to initiate recovery action, and/or to provide various kinds of assistance to the operator to reduce the recovery action initiation time.</p><p>To increase the time window, a promising measure is to substantially increase the separation distance between FPSO and tanker, e.g. from 80 m to 150 m. The feasibility of this measure is discussed from a number of perspectives. Recovery improvement gains are assessed. The key question concerning implementation is to know how much separation distance should be configured in the operation. This has to be based on considerations of both human operators’ need for reaction time, and tanker drive-off behavior. Parametric tanker drive-off motion simulations are carried out in which human action at various times are imposed. The necessary distance values to stop the tanker are then obtained, and ideally these should correspond to the separation distance values between FPSO and tanker in tandem offloading. These findings provide decision-making support to select an optimum field configuration for FPSO-tanker tandem offloading, which may inherently minimize the collision risk.</p><p>Effective reduction of reaction time can be achieved by early detection and/or quick decision-making. This is based on the operator information-processing model generalized earlier in this study. Measures to improve early detection are identified. Discussions are guided by the human signal detection theory, and supported by the operational facts of alarm and non-alarm signals in the operation. Measures to effectively reduce the operator’s time involved in diagnosis and situation awareness are also identified. They are theoretically built on the generic human decision-making theory, and specifically designed for drive-off intervention based on the facts collected via a questionnaire survey among shuttle tanker captains and DP officers. These findings illuminate a broad area in the human factor perspective, i.e. training, procedure, crew resource management, human-machine interface, and automation support, where measures to reduce operator reaction time should be targeted. These measures may directly reduce the FPSO-tanker collision risk in tandem offloading.</p>

Collisions between FPSO and shuttle tanker in tandem offloading operation have caused a growing concern in the North Sea. Several recent contact incidents between FPSO/FSU and shuttle tanker have clearly demonstrated a high likelihood of contact between vessels in tandem offloading. The large masses involved, i.e. the high potential impact energy, make the collision risk large. Traditional ship/platform collision frequency modeling may not be applicable in the tandem offloading context. Moreover, offshore quantitative risk analyses generally focus more on technical aspects, little on human and organizational aspects. This leads to a hardware-dominated risk reduction approach, and it has been proved not to be effective to mitigate risks involved in complex marine operations in general. Frequency modeling of collision between FPSO and shuttle tanker in offloading operation is carried out in this study. The collision frequency model is structured in two stages, i.e. the initiating stage and the recovery stage, where the former involves an uncontrolled forward movement of tanker, and the latter involves the recovery actions initiated from tanker and FPSO to avoid the collision. In the initiating stage, this study focuses on tanker drive-off forward scenarios. Macroscopically, the frequency of tanker drive-off ahead during offshore loading and specifically during tandem offloading is portrayed by statistical data from an earlier study, recent SYNERGI incident data, and expert judgments made by tanker DP operators. Relatively high frequency values of tanker drive-off in tandem offloading are found. Microscopically, the tanker drive-off ahead scenario is investigated by examining 9 such events in tandem offloading based on investigation reports, interviews and discussions with individuals who directly or indirectly were involved. Findings reveal that in order to effectively reduce tanker drive-off in tandem offloading, efforts should be targeted on minimizing those failure prone situations, i.e. the excessive relative motions (termed as surging and yawing) between FPSO and tanker. A simulation-based study is carried out to quantitatively assess and effectively minimize the occurrence of excessive surging and yawing events. Horizontal motions of FPSO and tanker in tandem configuration are simulated via a state-of-the-art time-domain simulation code SIMO. Findings demonstrate that excessive surging and yawing events can be effectively minimized via measures such as minimizing FPSO surge and yaw motions in offloading, coordinating mean heading between FPSO and tanker, and using the dedicated DP software with the tandem loading function on tanker. Ultimately, these measures may provide a sound operational environment where the possibility of tanker drive-off can be minimized. In the recovery stage, this study is focused on the recovery action initiated by the tanker DP operator. Possible recovery actions are identified and evaluated. Based on calibrated tanker motion simulations, the allowable time for DP operator to initiate recovery action, so that tanker can be stopped within a separation distance, e.g. 80 m to FPSO, is found to be critically short. A 3-stage information-decision-execution model is generalized to model the DP operator’s information processing stages regarding action initiation when in a drive-off scenario. Based on this human information-processing model, expert judgment by simulator trainer and questionnaire survey among shuttle tanker captains and DP officers are conducted, reasonable estimates of the time needed for action initiation are obtained. The estimates are found to be convergent to the facts in the incidents. Findings suggest that tanker DP operators in general need more time to initiate recovery action than the allowable time window, i.e. recovery failure is likely due to lack of reaction time. Two principal recommendations are proposed to reduce the recovery failure probability, i.e. to provide a longer time window for the operator to initiate recovery action, and/or to provide various kinds of assistance to the operator to reduce the recovery action initiation time. To increase the time window, a promising measure is to substantially increase the separation distance between FPSO and tanker, e.g. from 80 m to 150 m. The feasibility of this measure is discussed from a number of perspectives. Recovery improvement gains are assessed. The key question concerning implementation is to know how much separation distance should be configured in the operation. This has to be based on considerations of both human operators’ need for reaction time, and tanker drive-off behavior. Parametric tanker drive-off motion simulations are carried out in which human action at various times are imposed. The necessary distance values to stop the tanker are then obtained, and ideally these should correspond to the separation distance values between FPSO and tanker in tandem offloading. These findings provide decision-making support to select an optimum field configuration for FPSO-tanker tandem offloading, which may inherently minimize the collision risk. Effective reduction of reaction time can be achieved by early detection and/or quick decision-making. This is based on the operator information-processing model generalized earlier in this study. Measures to improve early detection are identified. Discussions are guided by the human signal detection theory, and supported by the operational facts of alarm and non-alarm signals in the operation. Measures to effectively reduce the operator’s time involved in diagnosis and situation awareness are also identified. They are theoretically built on the generic human decision-making theory, and specifically designed for drive-off intervention based on the facts collected via a questionnaire survey among shuttle tanker captains and DP officers. These findings illuminate a broad area in the human factor perspective, i.e. training, procedure, crew resource management, human-machine interface, and automation support, where measures to reduce operator reaction time should be targeted. These measures may directly reduce the FPSO-tanker collision risk in tandem offloading.

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Det hydro-pneumatiske strekksystemet til stiger&#248;rene virker som en passiv hivkompensator med en olje/gass-akkumulator for a utligne de relative bevegelsene mellom semien og stiger&#248;rene. Semiresponsen f&#248;rer direkte til at stempelet beveger seg i sylinderen, noe som gir kompressjon eller ekspansjon av gassen basert p&#229; ideell gasslov. Dette gir en ekstra ikkeline&#230;r stivhet, som ogs&#229; er avhengig av gassvolumet i systemet. Effekten av semiresponsen for et strekksystem med variabelt gassvolum har blitt evaluert.Str&#248;mmen av hydraulisk v&#230;ske mellom sylinderen og akkumulatoren i kombinasjon med str&#248;mmen av gass mellom akkumulatoren og gassreservoaret, gir visk&#248;s dempning i strekksystemet. Disse friskjonskreftene er bestemt av lengde og diameter i r&#248;rsystemet, ventiler og andre komponenter i det hydraulisk-pneumatiske systemet. I denne masteroppgaven er det brukt forenklede beregningsmodeller som gir gode, men ikke eksakte resultat. En numerisk metode har blitt skrevet for &#229; beregne trykktap basert p&#229; Bernoullis ligning og konservering av masse og moment i systemet.En numerisk metode har ogs&#229; blitt skrevet for &#229; l&#248;se svingeligningen i tidsdomenet med ikkeline&#230;r stivhet og dempning fra det hydro-pneumatiske strekksystemet. En sensitivitetsanalyse basert p&#229; forskjellige perioder og b&#248;lgeh&#248;yder ble gjort for &#229; separere de forskjellige bidragene fra stiger&#248;r-strekksystemet, og lettere finne trender og sammenhenger som definerer dette. I forprosjektet ble transferfunksjoner regnet ut for noen gitte senarioer. Disse gir viktig og mye brukt informasjon i tidlig designfase for prosjekter. Nye transferfunksjoner er tatt ut ved &#229; plotte maksimum respons i stabil fase, basert p&#229; tidsserier fra de forskjellige b&#248;lgeh&#248;ydene og periodene.Det finnes friskjonskrefter i ulike kontaktpunkter mellom bevegelige deler p&#229; semien, noe som er spesielt viktig for sm&#229; sj&#248;tilstander. Semiresponsen blir p&#229;virket av friksjonskreftene mellom stiger&#248;rene og kj&#248;lguiden, og i pakninger i strekksystem-sylinderene. N&#229;r friskjonskreftene blir st&#248;rre enn eksitasjonskreftene fra b&#248;lgene, vil semien bli &#171;forankret&#187; til stiger&#248;rene. Dette f&#248;rer til at b&#248;lgekreftene blir overf&#248;rt direkte til stiger&#248;rene, og denne belastningen kan redusere forventet levetid. Analyser har blitt gjort for hvilke regul&#230;rb&#248;lger dette vil skje. Det er ogs&#229; sett p&#229; hvordan den &#248;kte stivheten ved en &#171;forankret&#187; tilstand reduserer egenperioden til systemet.

A collection of life experiences, and inter-monologues that attempt to shed light on my artistic process.

This Master thesis details the development of a mathematical model of ROV SF30k, and its implementation into a DP control system developed by Espen Tolpinrud.The project was performed as a part of the Applied Underwater Robotics atNTNU.A 6DOF model of the ROV was developed. The parameters of the model werefound using both the 3D model of the ROV provided by Sperre AS, and based onthe parameters found previously for ROV Minerva. Both ROVs were developedby Sperre AS and share many similarities. Thrust configuration was developed forthe ROV based on the geometric positions and orientations of its thrusters, whilethrust coefficients were found using propeller data provided by Sperre AS. The DPcontrol system was configured to operate SF 30k by using a configuration file basedon the found parameters.A number of modules were ported from the old DP system, which was tailormadefor ROV Minerva, to the new one. This includes the Kalman Filter, controllersand thrust allocation. An adaptive passive nonlinear observer was developedand implemented.The existing simulator model for ROV Minerva was modified to be able tosimulate ROV SF 30k. This was done by changing the parameters of the processplant model and thrust dynamics.The parameters in the configuration file for the new control system were verifiedduring sea trials onboard R/V Gunnerus on May 29-30th 2012. The thrust allocationparameters were found to be satisfactory during ROV operation, however, themathematical model of the ROV could not be verified due to the small window ofoperation during the sea trials.

In view of the increasingly popular climate change debate worldwide, maritime transport is under pressure to create sustainable solutions for a cleaner future.One of these solutions is using liquefied natural gas (LNG) as ship fuel. LNG has a higher hydrogen-to-carbon ratio compared with oil-based fuels, which results in lower specific CO2 emissions (kg CO2/kg fuel). Other benefits of LNG are the total elimination of SOx emissions and particulate matter, and 85-90 % reductions in NOx emissions. DNV has estimated a net global warming benefit of 15 % with the use of LNG. However there is still a need to map the greenhouse gas emissions throughout the life cycle of LNG. This thesis is a Screening Life Cycle Assessment of LNG as fuel, with the main objective to carry out a life cycle analysis of the process &#147;Bunkering of LNG&#148;. Screening is a simplified LCA which aims at identifying the important parts of a life cycle, or so-called hotspots. Bunkering of LNG and the bunkering facility have been chosen as the hotspots in this analysis for their uniqueness. The processes related to bunkering have not been analysed at this level of detail in published literature. The LCA software GaBi Educational has been used to implement the bunkering model and analyse the life cycle inventory results. Processes related to energy use, manufacturing and direct emissions were included in the GaBi model. The CML 2001 method was used to assess the Global Warming Potential (GWP). This is the main characterisation factor of the environmental issue climate change, which was in focus in this analysis.The impact assessment showed that emissions related to manufacturing are the greatest contributors to the GWP, with a total GWP of 75 917 [kg CO2-Equiv]. Energy use contributes the least, with only 0,36 &#137; of the total impact, which is considered negligible. Direct emissions stand for 7 777 [kg CO2-Equiv] and is the only area of the bunkering life cycle where emissions can be considerably reduced. In fact, all direct emissions can be omitted by the use of BOG recovery strategies, such as vapour return. The conclusion drawn is that the emissions associated with bunkering of LNG is perhaps not the main issue. A more pressing issue at the moment is the low fuelling possibilities for LNG. If LNG is to become the fuel of the future, fuelling must be made more accessible and available.

Thèse de doctorat : Sciences de l'Environnement Marin : Aix Marseille 2 : 2002. / Thèse : 2002AIX22010. Bibliogr.: f.199-208.